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Straw Bale Construction

By: Chris Nickson - Updated: 6 Nov 2017 | comments*Discuss
 
Straw Bale House Foundation Anchor Bolts

People have built homes using straw, grass, or reed throughout history. During the late 1800s on the American plains however, straw bales houses were a matter of necessity; there was no lumber for construction. Now, with the rise in interest in sustainable housing, there's been a revival in straw bale construction. It's mostly been in the U.S., but in 1995, Bob Matthews, of the Institute for Social Inventions and author of The Complete Manual of Practical Home Building, built a straw cabin in the U.K. (possibly the first such building in Britain) and has been living in it ever since.

With straw often being a farm surplus product and very cheap (around 40p a bale, or £1.50 delivered), it's inexpensive, and an easily renewable medium. Properly built, straw bale houses are fire-resistant, waterproof and actually pest free, with super-insulated walls.

Construction Basics

You'll need about 300 standard three-wire bales of straw to make a 2,000 square-foot house (186 sq. metres). You skewer them on rebar pins (or wood or bamboo stakes) to keep them firm. When you've finished, after adding plumbing and wiring, you seal and finish the walls.

You need to use bales that have a uniform size (about a metre long, half a metre wide), are well secured with two strings, and with very few seed heads. Make sure they're compacted properly and dense - each bale should weight between 16-30 kilos - and dry (and be sure you keep them dry when you're building, for obvious reasons). Even after you've finished the house, you need to be certain the centre of the bales doesn't become wet through either the top or bottom - however, if the outside gets wet, that's fine; it'll dry out naturally.

Types of Construction

Use a "non-structural" or "in-fill" system for bigger structures. That means you make a frame first to support the roof, then pierce the bales with rebar as you rise, attaching the bales to the frame to keep your walls secure.

"Structural bale construction" is a little like Lego, where you stack the bales together in a "running bond" manner. After construction, you simply stucco the exterior and plaster the interior walls. However, since the bales compress as they settle, you need to leave settlement gaps above both windows and doors (how much depends on the number of bales).

Straw and clay construction is a little like cob. You mix clay and water, and then add straw, before packing it into a wooden frame.

Mortar bale construction is similar to working with giant bricks. You put mortar between the bales, and the mortar actually takes the wall's weight (it needs to be quite thick - at least an inch on all surfaces of the bale). It's a good method when you're making a two storey house or a basement. About the only drawback is that the mortar creates cold bridges and thermal leaks. Again, use stucco and plaster to add to the structural integrity.

Finally, there are also pressed straw panels. Here you use straw that's been compacted under pressure. You can also use the panels for floors and roofs if you wish.

Maintenance

In theory, at least, a properly constructed straw house, built where there's good drainage, could last for centuries. You should probably use a different material for the roof, however (something more permanent), and build that roof at a steep angle for drainage.

Foundation

If you're building a straw bale house in Britain, the climate means you'll have to be on a self-draining foundation (one of the best is a rubble trench). You'll also need plastic or metal strapping to attach the wallplate (use anchor bolts) to the foundation.

Make sure your foundation goes well below the frost line, and then fill it with small stones before you put concrete in the rest of the space. You also have to be sure that water can't gather at the point where the bales meet the foundation, which means you need to elevate the foundation by at least 23mm (much higher is better), and leave a good overhang (around 450mm) on the roof.

Finishes

Obviously, after you've completed the construction, you still need to render, or finish, the place. Limewash is good, but very expensive. Earth plaster is an American favourite and durable to use both inside and outside. It's non-toxic, and comes in many colours. Additionally, you have plenty of time to work it and it dries to a hard surface.

Rot and Pests

You shouldn't have a problem with rot as long as you use dry bales. Remember, though, that all the paint must be permeable so moisture isn't trapped in the wall. Believe it or not, you find fewer insects or vermin in straw bales than you do in wood, and once you've plastered the building, they can't get in.

Fire

You might also be surprised to learn that straw bale construction is very fire-resistant; in tests it actually out-performed conventional building materials. However, in spite of all its advantages, getting a mortgage for a straw bale house can be difficult as can insuring it.

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[Add a Comment]
Hello, I'm looking for suppliers of good quality straw bales in Pembrokeshire, does anyone have any tips?.We're near Lanycefn and need around 200 for an infill-type bale outbuilding.Any advice for hazel pole suppliers would also be appreciated, and lime plasterers (although I realise the window for lime plastering has closed for the winter). Thanks!
Rachel - 6-Nov-17 @ 5:08 PM
laurabale - Your Question:
Hi, to all those who are building in Cornwall..I am looking to learn about straw bale builds as I want to build my on house in the future. Id be happy to give my time and limited skills for some teaching, in the cornwall area. Hope this is of interest. Laura

Our Response:
Thanks Laura. If anyone wants to get in contact with Laura, please do so by emailing jmarshall@pts.com and we'll forward them on.
SustainableBuild - 19-Jun-17 @ 2:06 PM
Hi, to all those who are building in Cornwall........... I am looking to learn about straw bale builds as I want to build my on house in the future.Id be happy to give my time and limited skills for some teaching, in the cornwall area. Hope this isof interest. Laura
laurabale - 15-Jun-17 @ 6:52 PM
We are relocating to Cornwall and hope to enjoy a mostly self-sufficient lifestyle. I am a musician and my ambition is to build a single story straw bale building which will be a guest house come recording studio. My question regards planning permission and the chances of getting planning permission to do this. Does anyone have any experience of a similar project? Any advice, tips, would be most gratefully received. Thanks
Stratman - 7-Jul-16 @ 10:11 PM
Hello We are building a straw bale house in the Correze region of France. I need some advice as to where to source straw bales in France. Can anyone advise me? Thank you for your help L
landd - 26-May-16 @ 6:25 PM
Archie Mac phearsum- Your Question:
I am a straw bale lime plasterer and like to advice on the plastering to straw so their is no failure I've been strawbale nut for a over 20years and a recording studio is a great idea please contact me if need advice on lime plastering onto straw I have done a lot of strawbale projects

Our Response:
Thanks Archie, I've passed on your email address to the original poster hope that's OK.
SustainableBuild - 22-Apr-16 @ 12:16 PM
I am a straw bale lime plasterer and like to advice on the plastering to straw so their is no failure I've been strawbale nut for a over 20yearsand a recording studio is a great ideaplease contact me if need advice on lime plasteringonto straw I have done a lot ofstrawbale projects
Archie Mac phearsum - 21-Apr-16 @ 12:48 PM
Gordon - Your Question:
We are planning new music studios in SE London, and considering creating two large straw bale buildings –1 x 16mt x 11mt internal space, and the other 1 x 10mt x 7mt, both as a two storey build.We are practical, with wood working and building skills, so we could help as part of the construction team, although we will need one or two people with straw bale building experience to lead the project. The planned site is a yard and has a good solid concrete base 30/40 cm thick pretty much throughout. Not sure its self-draining however. Load in for materials is good and direct to site, with easy access for trucks & fork lift. This could be a very interesting project, so if anyone has suggestions on how to progress this plan further, please get in touch.Many thanks

Our Response:
If anyone wants to respond via the SustainableBuild team, they can send in their details to jmarshall@pts.com and we'll forward them on.
SustainableBuild - 21-Apr-16 @ 11:22 AM
We are planning new music studios in SE London, and considering creating two large straw bale buildings – 1 x 16mt x 11mt internal space, and the other 1 x10mt x 7mt, both as a two storey build.We are practical, with wood working and building skills, so we could help as part of the construction team, although we will need one or two people with straw bale building experience to lead the project. The planned site is a yard and has a good solid concrete base 30/40 cm thick pretty much throughout. Not sure its self-draining however... Load in for materials is good and direct to site, with easy access for trucks & fork lift. This could be a very interesting project, soif anyone has suggestions on how to progress this plan further, please get in touch. Many thanks
Gordon - 19-Apr-16 @ 5:36 PM
Hi x I have an old stone wood barn x I am looking to renovate it using straw bales, into a space for yoga and therapy x Do you know anyone in devon who would have some knowledge on straw bale building x thanks julie x
julie - 13-Apr-16 @ 10:00 AM
I am thinking about doing a barn conversion. The barn we are looking at is quite small so I would like to double it's size both downstairs and upstairs with a strew bale extension. Is this possible? Would it be possible to put one roof on the building? Thanks
strewbarn - 20-Feb-16 @ 5:53 PM
@Starman - we'll put this on our facebook page if you like.
SustainableBuild - 12-Feb-15 @ 2:08 PM
Hi, I hope you can help...I'm looking to find a supplier of construction grade straw bales in Cornwall. I have not been able to find any so far and I'm losing the will to live! Failing that, could you recommend a supplier that could also deliver to Cornwall? I look forward to your reply, Starman.
starman - 9-Feb-15 @ 10:52 PM
Hi I was wondering if anyone could help me with a topic im trying to do with my dissertation. The topic so far is based on whether straw bale construction has a major impact on sustainability? Is there any links you no that could help me with this research? Regards,
k lewis - 30-Jan-13 @ 10:38 PM
Hi I have a bisf property and have recently discovered that the ceiling has been insulated using straw I wanted to put spotlight on in the ceiling but am conscious about fire hazards is it possible to install spotlights within a straw insulated ceiling
Syeda - 21-Dec-12 @ 11:40 AM
Hi - I have an off grid water access property near Parry Sound Ontario. I will be building a 32' x 24' log & stick frame cottage in 2014 and am looking into "Sustainable Building" ideas-- I am thinknig of using straw bales only for the foundation - is this possible - the site location is high and dry - Thanks - Jimmy
Jimmy - 29-Oct-12 @ 6:37 PM
Can you recommend a builder who could build me a straw bale extension to my home in London? Thanks
Bass - 28-Oct-12 @ 2:38 PM
As the article states, you do need the right ground, and insurance will generally be problematic. You also need to be extremely careful not to construct the house in an area that’s prone to flooding and it would generally be destroyed, or at least rendered uninhabitable. If consider a straw bale house, take this into account.
David - 4-Oct-12 @ 10:53 AM
Hi Chris, I am working on research relating to the chronology of straw bale construction at the moment and I was wondering if you have any images of Bob Matthews' house or if you know a good way of contacting him? Haven't had much luck Googling 'Institute for Social Inventions' unfortunately! Any clues/leads greatfully received . . . Thanks, Oli
oli - 3-Apr-12 @ 11:44 AM
Interested in finding Areas that Are excepting Strawbail construction a Directory Ect.. Building Law.
Dan - 27-Feb-12 @ 2:10 AM
Hi, I'm interested in the response to jonneve's question as above, as I too want to add a straw bale construction to an already existing block wall. What is the best way to tie them in, given that the bales will compact somewhat ( it will only be a single storey and not very high) and just 32sq metres to mirror the existing building.Thanks for any help,Carole
Carole - 19-Sep-11 @ 2:29 PM
Hello, I'm looking for a bit of advice for building with straw bales, and I'm wonrdering if perhaps you could help.Basically, I've got an old stone house in France, which is made up of two unconntected buildings, that I would like to unite in order to make a coherent whole. I therefore need to make a new wall, about 8m long by 3m high, and I'm considering using straw bales. My question is the following : would it be possible for me to build with straw bales Nebraska style, ie without any wood structure, or would the junction of the bales with the stone walls be problematic? I'm concerned about the fact that the straw is likely to get compacted and to move, whereas the stone walls obviously won't, so I'm not sure the junction would be strong enough. I'm wondering if I could key the two walls into each other by having big stones jut into the straw wall, which in turn would probably require using mortar to give the straw bales extra strength and less risk of compaction. As you can see, I'm a bit confused. :) What do you think? Is there some way to make this work, or would a wood structure be necessary?
jonneve - 20-Jul-11 @ 11:16 AM
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